As Musk recently emphasized, though, that launch will be just the beginning of flight testing, and there’s a “good chance that the vehicle does not make it into orbit” on the first try.

It’s also worth noting, as The Verge has, that the Falcon Heavy has already had tentative launch targets that didn’t come to fruition. In 2011, for instance, Musk said the Falcon Heavy would launch in “2013 or 2014.”

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Joining a tradition of Muskian optimism, the Heavy turned out to be a much bigger engineering challenge than anticipated. It has 27 engines, three times as many as SpaceX’s Falcon 9, and all of those engines have to be carefully synchronized for a successful launch. But the firmer target date, and recent milestones including a test-fire of a booster on the ground, suggest things are on track this time around.

The Heavy needs all those engines to deliver its 54-ton payloads, potentially including human crew and infrastructure for crewed bases, as far as Mars. Earlier this year, SpaceX pushed back its target date for the first Mars missions from 2018 to 2020.

(Musk’s colonization road map also includes an even bigger rocket, with 550 metric tons of orbital lift, but it’s still in early development.)

Most importantly for SpaceX’s plans, the Falcon Heavy, like the Falcon 9, will have reusable components that land intact on Earth after launch. Re-use is projected to drastically reduce launch costs, but even after success with the Falcon 9, that trick could be several years coming for Falcon Heavy.